Enable Yum Repositories on CentOS

NB: This may break your install if they've been disabled for a reason e.g. on a bespoke Linux

If the yum repos containing the packages you need are disabled by default:

1. Find the version of CentOS:
   cat /etc/issue
2. List the installed repos:
   yum repolist all
3. Enable the repository in the config file e.g.:
1. Copy original:
   cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.orig
2. Edit file:
   vi /etc/yum.repos.d/CentOS-Base.repo
3. Initiate INSERT mode: i
4. Make necessary changes in the first repo:
   Uncomment (remove #) from baseurl=http
   Replace centos/$releasever with the version e.g. centos/7.2.1511
   enabled=1
4. Update the repositories:
   yum update
5. Install yum-utils:
   
   yum install yum-utils